Measurement of oxidation reduction potential in ore beneficiation

ABSTRACT

Oxidation-reduction potential of a beneficiated ore slurry prepared for flotation is determined under optimum flotation conditions and the slurry thereafter is treated with beneficiating chemical in quantity controlled to the range of the pre-determined oxidation-reduction potential.

United States Patent 1 1 1111 3,883,421

Cutting et al. May 13, 1975 MEASUREMENT OF OXIDATION 2,651,413 9/1953 Daman 209/168 REDUCTION POTENTIAL [N ORE 3,051,631 8/1962 Harbin 204/195 X 3,094,484 6/1963 Riz0-Patr0n..... 209/164 BENEFICIATION 3,421,850 1/1969 Peterson 1 204/1 T [76] Inventors: Dale Emerson Cutting, PO. Box 3,486,847 12/1969 Steinhausen 204/1 T X 717; Richard Aflhmwomack 3,501,392 3/1970 Ayers 204/1 T Box 2 5 Joseph Vernon G ffi 3,735,931 5/1973 Weston 209/3 BOX all Of Cuba, FOREIGN PATENTS OR APPLICATIONS 87013 1,059,476 2 1967 United Kingdom 75/2 1 1 pp 288,306 Chen Abst., 66, 1967, 1071211 Chen Abst., 68, 1968, 71368N 52 us. c1. 209/1; 209/166; 75/2; Chen Absn. 7 1970, 1 114 8 204/1 T Chen Abst., 75, 1971, 24097M [51] Int. Cl 803d 1/02 [58] Field of Search 209/166, 167, 2, 1, 3, Primary ExaminerRobert Halper 75/2 [57] ABSTRACT Oxidation-reduction potential of a beneficiated ore [5 6] References Cned slurry prepared for flotation is determined under opti- UNITED STATES PATENTS mum flotation conditions and the slurry thereafter is 1.236.504 8/1917 Van Arsdale 423/26 X treated with beneficiating chemical in quantity con- 1.334.734 3/192 ompson 209/166 trolled to the range of the pre-determined oxidation- 1,335,000 3/1920 Houland 209/166 x reduction pmemial. 2,184,115 12/1939 Coke 209/168 2,607,718 8/1952 Suthard 137/93 x 20 Claims, 2 Drawing Figures TAILING TO CONCENTRATE STORAGE dim;

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saw 2 or 2 1 MEASUREMENT OF OXIDATION REDUCTION POTENTIAL IN ORE BENEFICIATION This invention relates to ore beneficiation to separate mineral values by flotation in maximum yield and economy by precise measurement of the need and control of supply of beneficiating chemicals to a fine ore slurry in water, in response to optimum oxidation-reduction potentials of the ore flotation suspension for effecting the separation.

More particularly, the invention is directed, in preferred aspect, to treatment of an ore containing sulfidable values to be separated by flotation from gangue materials economically in optimum yield by supplying sulfiding chemicals to the ore slurry in quantity controlled to develop an optimum range of pre-determined oxidation-reduction potentials as the mixture passes a selected control point such as through a flotation cell.

Mineral values to be separated from gangue materials in an ore by flotation, such as sulfide minerals, usually contain other mineral values desirably separated with the natural mineral sulfides, such as oxides, hydroxides, carbonates, sulfates, native metals and complexes thereof. These constitute common sulfidable ore components with which the sulfides may occur in the ore and are desirably recovered with the naturally occurring sulfides. The common practice in the art has been to add to such ores a sulfiding agent such as sodium sulfide, sodium bisulfide or hydrogen sulfide together with flotation chemicals, flocculants, etc. These sulfiding agents react at least superficially with such sulfidable mineral components of the finely ground ore particles to form a thin or superficial sulfide coating on some of the particle surfaces sufficient to improve their wettability by the flotation agent and thus tend to become more separable in the flotation as a froth, together with the normal sulfide values of the ore.

The difficulty has been that the sulfidable components for which a sulfiding agent is added to the ground ore slurry before flotation may vary in quantity in the ore being processed and will vary in size range and in particulate surface exposure in the batch under process, so that there may be too little or too much sulfiding agent supplied as the processing continues. There is some tendency to add an excess merely to effect the superficial sulfide coating needed for flotation; but this would involve substantial losses in economy. The ore fines mixture with sulfiding chemical and the need for even distribution of these chemicals among the fines variably sized for sulfiding has also resulted in substantial losses of recoverable values by some excess and some inadequate chemical treatment to effect optimum high flotation yields of the recoverable values present in the ore.

According to the present invention the quantity of benificiating chemical, typically sulfiding agent added to the ore to improve flotation, and sometimes including the quantity of flotation agent used, is precisely controlled in supply of these chemicals to a continuous flotation mix by varying the quantity responsively to maintain an optimum oxidation-reduction potential in the flotation cell. More practically, the quantity of sulfiding agent and usually flotation agent is variably supplied to the ore slurry to be processed as needed to maintain a selected range of the developed oxidationreduction potential in the flotation cell, the selected range being optimum for the specific ore being treated.

Thus in an ore, wherein the recoverable value is, for example, substantially in the form of copper sulfide to be separated by flotation, and in which the ore also contains oxidized copper values such as cuprite, malachite or azurite, or mixtures thereof, whereby the copper sulfide is a natural mixture with copper oxide, copper carbonate or copper hydroxide, or mixtures thereof, and also sometimes to a minor extent, copper sulfate and native copper, and which is usually further admixed with gangue materials, typically sandstone and harder rock matrices, the ore must first be ground to substantially release the mineral values in small particle form. The ore may, for example, be ground by milling to a range of about to 200 microns, a sieve size of about 30 to l40 mesh U.S. standard sieve. The ground ore fineness is sufficient to allow reaction and superficial coating of the sulfidable components with a sulfide film formed in reaction with the sulfiding agent upon these known sulfidable forms of copper, thereby modifying the particle surfaces with sulfide film. Such surfaces so modified allow wetting with the sulfide selective flotation agent for separation of the sulfide coated copper values along with the native copper sulfide by flotation. it is found that this superficial film in combination with other variable components of the flotation mixture such as the air introduced into the cell to effect the flotation, the degree of reaction of the sulfidable component upon the recoverable values and the conductive character of the flotation agent per se, all present in the liquid and air suspension in the flotation cell, will develop a measureable oxidation-reduction potential which, according to this invention, applicants use as a guide to determine whether this mixture as supplied to the flotation cell will allow optimum separation of the mineral values by flotation. Thus, applicants use the oxidation-reduction potential as a basis upon which to adjust the chemical supply to the ore slurry to effect optimum separation.

In setting up the present process an ore body is crushed and then ground and classified to a flotable slurry in water. It is then treated with beneficiating chemicals such as flotation agents; and, where the ore is of a mixed type, with a sulfiding agent to improve flotation of non-sulfide values occurring in the mixed ore body. These chemicals are supplied in quantity found by analysis to be usually optimum for floating the total mineral substance desirably recovered in the ore. The slurry is also treated with the optimum quantity of flotation agents and other usual beneficiating substances i.e. aerofloat, flocculant, superfloc, etc., commonly added to the ore in preparation for flotation, the mixture being then passed to a flotation cell such as a commerical Maxwell cell. Air in controlled quantity is also admitted to the cell, mixing with the slurry in conventional manner to float the mineral values.

An electrolytic voltaic cell of any commercial type such as a standard cell of calomel-platinum electrodes, is mounted in contact with the aerated slurry with the electrode dipping into or in conductive contact with the slurry at a selected reference point, preferably near the top of the flotation cell in a manner such that the slurry is made the electrolyte of the cell whose EMF is measured usually in millivolts by leads connected to the electrodes and to a voltmeter. Thus the measured EMF of the cell is that produced by the flotation slurry per se as it continuously flows by and the EMF output of the cell thus formed is the oxidation-reduction potential and it will vary with the condition of the flowing slurry. It will vary with the mineral content, its particle size, the type and quantity of the benificiating such as sulfiding or flotation chemicals used with the quantity of air and the homogeneity of the mixture, Other factors such as temperature will also have an effect upon the EMF.

The efficiency of the flotation over a series of tests is noted, particularly the variation in oxidationreduction potential of the cell is measured with these several variants, such as by slightly varying the quantity of ore beneficiating and flotation chemicals as needed, and determining the approximate optimum recovery of metal values from the ore with respect to quantities of beneficiating chemical, and recording the oxidationreduction potentials of the cell developed over such range of operating conditions. In this manner the optimum yield of a flotation cell with variable quantities of beneficiating chemical is determined in terms of the oxidation-reduction potential developed in the flotation slurry being treated. An optimum specific oxidation-reduction potential for treating a particular ore will be found but, more practically, a narrow range of oxidation-reduction potential values will be found for most efficient operation of the flotation cell making minor allowances for some variables.

Thereafter, having first determined optimum conditions from an ore body of substantially constant composition, according to the test values developed with a fixed quantity of beneficiating chemical, the normal supply as well as flotation agent, etc., it then becomes possible to operate the total beneficiating system in terms of the continued EMF readings available as the desired range of oxidation-reduction potentials needed for operation of the flotation cell.

For example, it may be noted in beneficiating treat ment of an ore body containing between A and l percent of copper values including sulfidable components that it requires a feed of between l and 2 pounds per ton of sulfiding agent such as sodium sulfide and be tween 0.1 and 0.3 pounds per ton of a xanthate flotation agent for optimum removal of copper values from such ore in which from 0.5 to 0.1 per cent of the copper is an oxide to be sulfided. For instance, such ore efficiently treated in a flotation cell aerated with air for efficient removal of copper forms as a froth would develop an optimum oxidation-reduction potential in the ore slurry during normal flotation operation of the cell in the range of I25 to 160 millivolts, preferably 135 to 155 millivolts as the slurry flows through the Maxwell cell. The ore body, however, continuously fed through the Maxwell cell, will vary. The cell output will also vary with the variation of the feed. This variation in the actual composition of the ore being milled, and the actual quantity of sulfiding agent needed, and preferably also the actual quantity of flotation agent needed, are also varied in supply to the feed. According to this in vention, such variation of beneficiating chemicals is made in quantity needed to maintain the cell potential within the above stated range; that is, to maintain an oxidation-reduction potential within the Maxwell cell in the determined optimum range. When the oxidation reduction potential reads below that pre-determined value or above the value of the selected range, the feed of the beneficiatng chemicals supplied to the ore slurry is varied, modifying such quantity so as to maintain the oxidation-reduction potential of the cell in the preferred acceptable range.

As is known, secondary flotations are usually performed on several flotation cells mounted in a series, such as Fagergren cells, which perform a secondary flotation. These, too, need to have an adjusting supply of beneficiating chemical, usually both the sulfiding as well as flotation agent adjusted for optimum conditions for the secondary cell. Consequently, these, too, will have the beneficiating chemical added, but again such supply to the secondary cells is also at a rate to maintain a selected oxidation-reduction potential range in each of the secondary cells.

The invention is further described in relation to the drawings wherein:

FIG. 1 shows an ore beneficiating flow sheet; and

FIG. 2 shows a system in which the feed of ore beneficiating chemical may be automatically controlled in selected quantityv Referring first to FIG. 1, crushed ore fines comprising about 40 percent solids crushed initially to coarse fragments of which about percent of three-eighths inch or less enters the system conveyor line 10 and is passed to a ball mill I2 by way of a hopper l4, and is milled in water to a slurry with particles ranging in size from about to 200 microns. The slurry is continuously withdrawn from a collection box 16 by way of a pump 18 controlled by a density meter 20, passing to a classifier 22 in which the selected oversize of particles are returned to the hopper 14 by way ofline 24 and the slurry of fines, controlled in size for flotation, pass by way ofline 26 to a distributor box 28. The slurry is then divided, passing by way of lines 30 and 32 to Maxwell cells 34 and 36, respectively.

Beneficiating chemical solution, which for a copper ore identified above would comprise sulfiding agent, flotation agent, flocculating agent, etc., is supplied to each line 30 and 32 for treatment of the slurry passing therethrough, the chemical for line 30 entering by way of line 35 and the chemical for line 32 entering by line 37, each at a rate controlled by valves 39 and 41, re spectively. Flotation air is also supplied at any usual point of the system indicated only diagrammatically at 38 and 40. Oxidation-reduction primary cells 42 and 44 which may be standard calomel-platinum electrode cells are mounted with their electrodes dipping in the flotation slurry near the tops of each Maxwell cell 34 and 36. The voltage output of standard cell 42, by way of electrical lines 43, is indicated on a millivolt meter 47 and the output of cell 44 by way of line 45 is measured by voltmeter 49.

The quantity of beneficiating chemical added through lines 35 and 37 may be respectively controlled manually by adjustment of valves 39 and 41, passing a solution of necessary chemicals in adjusted quantity into the flotation slurry as it passes through lines 30 and 32, respectively, the quantity of chemical fluid being adjusted to flow therein at a rate to maintain the volt meter readings 47 and 49 at the pre-selected relatively constant millivolt values within a pre-selected narrow range. In this manner the oxidationreduction potential of cells 34 and 36 are maintained at the selected narrow range values of the meter readings 47 and 49 by adjustment of the supply beneflciating chemicals, each controlled by valves 39 and 41.

The floated mineral values of the Maxwell cells 34 and 36 are withdrawn from line 51 and, as mentioned Examples 1 and I] below, may be handled as separated mineral concentrate without further treatment. As shown in FIG. 1, the concentrate in line 51 can be passed to the second Fagergren cell 54. The residual slurry withdrawn by way of lines 46 and 48 may pass by way of line 50 to the first cell 52 of of the series of Fagergren roughers; at least the first two of which 52 and 54 have mounted similar primary cells 56 and 58, each connected by lines 60 and 62 to millivolt meters 64 and 66, respectively. Tailings are withdrawn by line 72 from an after portion of the last Fagergren. In this manner the floated concentrate separated as the froth in the Maxwell cells may also be passed by line 51 in a series through Fagergren rougher cells 54 and 68 and finally out of the system by way of cell 68 and outlet 72. The flotation slurry in line 50 enter the first Fagergren cell 52 and leaves the system from cell 68. The mineral values as concentrate overflow the cells into a launder 71 and leaves by way of line 70 for further thickening, filtration and then storage as concentrated ore values ready for further refining. The tailings leave the Fagergren rougher cell 68 by way of line 72 for further disposal.

As in the preliminary flotation, the further treatment in the Fagergren cells is controlled by primary cells 56 and 58, each mounted near the top of a Fagergren 52 and 54 to measure the oxidation-reduction potential in the slurry in each of these cells. Thus the entering slurry in line 50 is floated in Fagergren 52 and has its oxidation-reduction potential measured in millivolts at this point by the primary cell 56 which is indicated as EMF upon meter 64. Additional beneficiating chemical and flotation agent is supplied to line 50 by way of a supply pipe 74 controlled by a valve 76 and the quantity of chemical added is a small adjustment of the system responsive only to maintain the optimum voltage indicated in meter 64. Again, last traces comprising comparatively smaller quantities of beneficiating chemical is supplied by way of line 78 controlled by a valve 80 which adds the chemical to the floated slurry just before it enters the second Fagergren 54. This supply of chemical is also made controllable to the EMF reading on meter 66 responsive to the current developed in the electrolytic cell 58 mounted similarly near the top of the Fagergren 54. The necessary supply of air to the rougher flotation cells 52 and 54 enters through any conventional point 40. In this manner, both at the primary flotation Maxwell cells, as well as the secondary flotation Fagergren cells, beneficiating chemical is supplied in exact quantity by control of valves 39, 41, 76, and 80, each manually or automatically set to supply sufficient beneficiating chemical response to the oxidation-reduction potential developed in each flotation cell, according to a predetermined EMF range.

The system may be made entirely automatic, if desired, and a diagrammatic arrangement which effects this is shown in FIG. 2. FIG. 2 shows in plan the Maxwell cells 34 and 36, each having primary cells 42 and 44 mounted near its top, their respective outputs being connected by lines 43 and 45 to meters 47 and 49. Meter 47 in turn is electrically connected by control line 82 to a solenoid 84 having an armature 86 which controls the flow of beneficiating chemical fluid through valve 39 to the Maxwell 34 by way of line 20. Similarly the meter 49 output current is connected by control line 88 to a solenoid 90 having an armature 91 mounted connected to control the flow of beneficiating chemical through valve 41 to Maxwell 36 by way of line 32. An original make-up tank 92 contains a mixture of beneficiating chemical 94 in controlled concentration for supply to the system. A pump 96 is mounted to pump liquid chemical from the tank 92 and pass the same to a supply pipe 98 for supply of the system with the beneficiating and usually also flotation. chemical 94 under a controlled flow pressure. The supply pipe 98 joins valve 39 as its supply of fluid and the solenoid 84 controlled quantity of fluid passing to valve 39, passing the requisite quantity of chemical to line 30 responsive to solenoid 84 movement and the EMF of the cell 42. Similarly, line 98 also passes liquid chemical supply to valve 41, which supplies slurry carrying line 32 with a controlled quantity of beneficiating chemical as it passes to Maxwell cell 36 responsive to the current developed in the cell 44 mounted therein. Again the current developed in cell 56 mounted in the first Fagergren 52, in turn measured in the meter 64 and controlling solenoid 104, controls valve 76 to pass chemical through lines 74 and 106 in response to the EMF developed in meter 64, as the oxidation-reduction potential of the Fagergren 52. Valve 76, so controlled, draws a supply of beneficiating chemical from the supply line 98, passing the same into the entering slurry of the Fagergren 52. Similarly, the valve is controlled by primary cell 58 and meter 66 to control the supply of chemical to Fagergren 54, drawing the same from supply line 78 connected to the source 98 in response to the setting of solenoid 108 controlled by the meter output 66.

In operation it will be seen that the quantity of chemical to each cell is automatically controlled to pass the chemical from the main supply line 98 into flotation slurry lines passing respectively to cells 34, 36, 52 and 54 in response to the respective oxidation-reduction potentials developed and measured in each of these cells. The quantity of the chemical is that needed by each cell and automatically supplied according to its oxidation-reduction potential of the particular flotation cell.

The invention is further illustrated by way of the following examples:

EXAMPLE I A sand deposit of oxide copper having an overall copper content of 0.7 percent of which the copper value is approximately 25 percent copper sulfide and the remainder being an oxidized form of copper, such as malachite, azurite or cuprite, ground to pass an 80 mesh screen, U.S. standard sieve, is passed as slurry comprising 40 percent solids to a Maxwell cell together with potassium amyl xanthate solution of 0.4 pounds per gallon and aerofroth 65 and 70, and 12.5 percent solution of sodium sulfide. The characteristics of the copper are such that the ratio of the oxidized copper to the copper sulfides will vary continuously in a very minor range from batch to batch as the product is mined and milled.

The sodium sulfide solution is passed into the Maxwell cell at a rate of l3,000 milliliters per minute together with xanthate solution at 13,500 milliliters per minute for a period of 24 hours without variation of this constant feed. At the end of this period it was found that 59 percent of the total copper content was recovered using a total feed of sodium sulfide of 1.3 pounds per ton of ore fed and for the xanthate a feed of 0.22 pounds per ton.

EXAMPLE ll Using the same feed in described in Example I, but varying the quantity of sodium sulfide and xanthate solutions, while measuring the oxidation potential of the cell as the slurry was floated, and varying the quantity of both sodium sulfide and xanthate solution added as the froth flotation proceeded, to maintain the oxidation-reduction potential substantially constant at about l45.0 millivolts, it was found that for the same 24 hour period, at the same flow rate, that the copper recovery ws 63.2 percent, and the average consumption of sodium sulfide was [.18 pounds per ton and the xanthate was 0.19 pounds per ton.

EXAMPLE Ill The method as disclosed in Example ll was repeated, but controlling the oxidation-reduction potential in both Maxwell cells and subsequent Fagergren cells to approximately 155 millivolts by addition of sufficient and variable quantities of sodium sulfide and xanthate solution in each cell as the flotation proceeded, to maintain a substantially constant millivolt potential. It was found that the total recovery of copper was 65.5 percent and the total consumption of sodium sulfide was found to be 1.22 pounds per ton and the xanthate was 0.20 pounds per ton.

EXAMPLE IV The method as disclosed in Example I] was repeated, controlling the millivolt potential to 135.0 in each cell while adding H 8 in the amount of 0.32 pounds per ton of ore and xanthate in the amount of 0.20 pounds per ton. Recovery of the copper was 64.5 percent.

EXAMPLE V The method as disclosed in Example IV was repeated, controlling the millivolt potential to l40 millivolts in each cell, while adding N HS in the amount of 0.90 pounds per ton of ore. Recovery of the copper was 65.5 percent.

While the system is described with respect to a most common non-ferrous metal such as copper, it will be applicable to other metals, particularly those usually purifiable by flotation and particularly those minerals whose ores are usually available as sulfides, sometimes admixed with oxides, hydroxides, carbonates or the like. Such other metals include silver, lead, zinc, molybdenum and other typical metals usually concentratible by flotation. The method is also applicable to certain ferrous metal ores such as manganese, cobalt, cadmium, oftimes further in admixture with copper and sometimes with small quantities of native metals. Again, while for copper beneficiation such chemicals are used as would tend to convert the copper to sulfide ores, beneficiating chemicals for recovery of other metal values as would be better suited to such other ores would be used where the metal being recovered is not primarily copper.

While a standard cell, usually platinum-calomel mercury electrodes have been used for indicating EMF, any other primary voltaic cell capable of developing an easily measured EMF between electrodes, using the flotation slurry as electrolyte may serve as an EMF indicator. as control for operation of the flotation process, using the developed oxidation-reduction potential of such cell as control. Such other cells will be equally useful when standarized to an EMF output indicative of optimum operation of the flotation process under its control whereby the beneficiating chemicals may be varied by such EMF output as a control to effect opti mum operation.

Again, while it is convenient to control the addition of sulfiding agent for copper, as well as flotation agent added as a single solution, comprising the total beneficiating chemical substance added, it is possible to add the beneficiating chemicals separately and to control the quantity of each so added also in terms of the effective oxidation-reduction potential resulting from its addition in correct quantity. Moreover, some flotation agents, for instance, the xanthates, may inherently have a modifying effect upon the sulfidable surface of ore particles, so that where a sulfiding agent is added, apart from such flotation agents, the oxidation-reduction po tential developed by each will differ from that usually used for their composite where added together. Hence, the initial control may be established either upon the mixed beneficiating chemical solution and the best quantity thereof added will be responsive to the single control. When separate independent chemical solutions are added, each then is independently controlled in a range developed for each added independently.

Other modifications of this process variable with the normal flotation practice for each ore will occur to those skilled in the art for use in the present invention using the oxidation-reduction potential as a guide for controlled supply of such beneficiating chemical to control the flotation of such ore. lt, accordingly, is intended that the description herein be regarded as exemplary and not limiting except as defined in the claims appended hereto.

What is claimed is:

1. In a system for the beneficiation of an ore slurry over a range of compositions of the ore body from which said slurry was derived by addition to said slurry of a chemical substance of an oxidizing or reducing character including froth flotation agent and a flotation collector to improve the continuous separation of mineral values from said slurry by treatment including the step of froth flotation, the improvement comprising measuring the range of oxidation-reduction potentials of the said chemically treated slurry developed in efficient operation of said system as it is varied with variations of said ore body to define a preselected range of optimum potentials, and supplying said chemical substance to the slurry in quantity controlled to maintain the oxidationreduction potential of said slurry in said preselected range during the flotation step of said treatment.

2. In the beneficiation of an ore slurry by addition thereto of chemical substance to improve the separation of mineral values from said slurry by froth flotation, the improvement comprising pre-determining a range of oxidation-reduction potentials developed in a slurry of the ore beneficiated to a condition of high flotation yield of mineral values therein, and then modifying the quantity of beneficiating chemical substance supplied to said slurry to continuously maintain an oxidation-reduction potential of said slurry in the same pre-determined range as the flotation proceeds.

3. The method as defined in claim 2 wherein at least a portion of the chemical substance added reacts with the mineral values in the ore slurry to improve its flotation yield.

4. The method as defined in claim 3 wherein at least a portion of the chemical substance added is a flotation agent.

5. The method as defined in claim 3 wherein at least a portion of the mineral values to be recovered by flotation are sulfidable, and the chemical substance added to improve the separation of the mineral values from said slurry includes a sulfiding agent.

6. The method as defined in claim 5 wherein the sulfiding agent is a member of the group consisting of hydrogen sulfide, alkali metal hydrosulfide and alkali metal sulfide.

7. The method as defined in claim 6 wherein the alkali metal component of said alkali metal sulfides is sodium.

8. The method as defined in claim 2 wherein the flotation of said slurry to recover mineral values from the ore is performed by flowing said slurry through several of a series of flotation cells, each cell having a predetermined range of oxidation-reduction potentials developed for the slurry beneficiated to a condition of high flotation yield of mineral values for that cell, and the quantity of beneficiating chemical supplied to the slurry of each cell is adjusted to maintain the said range of pre-determined oxidation potentials for that cell.

9. The method as defined in claim 2 wherein the quantity of beneficiating chemical added to said slurry is manually controlled to maintain the oxidationreduction potential measured in the flotation cell in said pre-determined range.

10. In a system for the beneficiation of a copper ore comprising copper sulfide and other sulfidable particles of copper mineral by addition to a slurry of said ore of oxidizing or reducing chemical substances as well as of flotation collectors, flocculants and frothers and including a sulfiding agent to improve the separation of the copper mineral values from said slurry by froth flo tation, the improvement comprising pre-determining a range of oxidation-reduction potentials developed in a slurry of the ore beneficiated with said chemical substances to a condition of high flotation yield of mineral values therein, and then modifying the quantity of said beneficiating chemical substances supplied to said slurry to continuously maintain an oxidation-reduction potential of said slurry in the same pre-determined high flotation yield range as the flotation proceeds.

11. The method as defined in claim 10 wherein the sulfiding agent is selected from the group consisting of hydrogen sulfide, alkali metal hydrosulfide and alkali metal sulfide.

12. The method as defined in claim 11 wherein the alkali metal component of said alkali metal sulfides is sodium.

13. The method as defined in claim 10 wherein the sulfiding chemical component is sodium sulfide.

14. The method as defined in claim 10 wherein the flotation collector is an alkyl xanthate.

15. The method as defined in claim 10 wherein the flotation of said slurry to recover mineral values from the copper ore is performed by flowing said slurry through several of a series of flotation cells, each cell having a pre-determined range of oxidation-reduction potentials developed for the slurry beneficiated to a condition of high flotation yield of mineral values for that cell, and the quantity of beneficiating chemical supplied to the slurry of each cell is adjusted to maintain the said range of pre-determined oxidationreduction potentials for that cell.

16. The method as defined in claim 10 wherein the flotation of said slurry to recover mineral values from the copper ore is performed by flowing said slurry through a series of several flotation cells, each operating to remove mineral values by flotation, the first cell being a Maxwell cell for effecting primary recovery of the mineral values and the subsequent cells of the series being Fagergren cells operative to clean up additional values by flotation from the remaining ore slurry, each cell having the oxidation reduction potential of its slurry, the continuously flowing ore slurry therein continuously measured, and the beneficiating chemical added to the slurry passing to each of said cells being independently varied in quantity to maintain the preselected oxidation-reduction potential for each cell.

17. The method as defined in claim 16 wherein the requisite quantity of beneficiating chemical added to each cell is automatically controlled to be independently supplied to the slurry being floated in each cell in quantity responsive to the pre-selected range of oxidation-reduction potentials of each cell of said senes.

18. The method as defined in claim 10 wherein the copper ore is predominately sulfidable compounds of copper other than copper sulfide.

19. The method as defined in claim 10 wherein the copper ore is predominately oxides of copper.

20. In a system for the beneficiation of a copper ore comprising copper sulfide and other sulfidable particles of copper mineral by addition to a slurry of said ore of oxidizing or reducing chemical substances as well as of flotation collectors, flocculants and frothers and including a sulfiding agent to improve the separation of the copper mineral values from said slurry by flotation, said froth flotation being performed in a series of flotation cells, said beneficating chemical substances being added to said ore slurry to adjust its flotation condition in each flotation cell, the improvement comprising predetermining a range of oxidation-reduction potentials developed in the slurry of the ore being benificiated with said chemical substances to a condition of high flotation yield of mineral values for each cell, and then controlling the quantity of said beneficiating chemical substances supplied to said slurry passed to each cell to maintain an oxidation-reduction potential of said slurry in each cell in the said predetermined high flotation yield range as the flotation proceeds.

i l I. i l 

1. IN A SYSTEM FOR THE BENEFICIATION OF AN ORE SLURRY OVER A RANGE OF COMPOSITIONS OF THE ORE BODY FROM WHICH SAID SLURRY WAS DERIVED BY ADDITION TO SAID SLURRY OF A CHEMICAL SUBSTANCE OF AN OXIDIZING OR REDUCING CHARACTER INCLUDING FROTH FLOTATION AGENT AND A FLOTATION COLLECTOR TO IMPROVE THE CONTINUOUS SEPARATION OF MINERAL VALUES FROM SAID SLURRY BY TREATMENT INCLUDING THE STEP OF FROTH FLOTATION, THE IMPROVEMENT COMPRISING MEASURRING THE RANGE OF OXIDATION-REDUCTION POTENTIALS OF THE SAID CHEMICALLY TREATED SLURRY DEVELOPED IN EFFICIENT OPERATION OF SAID SYSTEM AS IT IS VARIED WITH VARIATIONS OF SAID ORE BODY TO DEFINE A PRESELECTED RANGE OF OPTIMUM POTENTIALS, AND SUPPLYING SAID CHEMICAL SUBSTANCE TO THE SLURRY IN QUANTITY CONTROLLED TO MAINTAIN THE OXIDATION-REDUCTION POTENTIAL OF SAID SLURRY IN SAID PRESELECTED RANGE DURING THE FLOTATION STEP OF SAID TREATMENT.
 2. In the beneficiation of an ore slurry by addition thereto of chemical substance to improve the separation of mineral values from said slurry by froth flotation, the improvement comprising pre-determining a range of oxidation-reduction potentials developed in a slurry of the ore beneficiated to a condition of high flotation yield of mineral values therein, and then modifying the quantity of beneficiating chemical substance supplied to said slurry to continuously maintain an oxidation-reduction potential of said slurry in the same pre-determined range as the flotation proceeds.
 3. The method as defined in claim 2 wherein at least a portion of the chemical substance added reacts with the mineral values in the ore slurry to improve its flotation yield.
 4. The method as defined in claim 3 wherein at least a portion of the chemical substance added is a flotation agent.
 5. The method as defined in claim 3 wherein at least a portion of the mineral values to be recovered by flotation are sulfidable, and the chemical substance added to improve the separation of the mineral values from said slurry includes a sulfiding agent.
 6. The method as defined in claim 5 wherein the sulfiding agent is a member of the group consisting of hydrogen sulfide, alkali metal hydrosulfide and alkali metal sulfide.
 7. The method as defined in claim 6 wherein the alkali metal component of said alkali metal sulfides is sodium.
 8. The method as defined in claim 2 wherein the flotation of said slurry to recover mineral values from the ore is performed by flowing said slurry through several of a series of flotation cells, each cell having a pre-determined range of oxidation-reduction potentials developed for the slurry beneficiated to a condition of high flotation yield of mineral values for that cell, and the quantity of beneficiating chemical supplied to the slurry of each cell is adjusted to maintain the said range of pre-determined oxidation potentials for that cell.
 9. The method as defined in claim 2 wherein the quantity of beneficiating chemical added to said slurry is manually controlled to maintain the oxidation-reduction potential measured in the flotation cell in said pre-determined range.
 10. In a system for the beneficiation of a copper ore comprising copper sulfide and other sulfidable particles of copper mineral by addition to a slurry of said ore of oxidizing or reducing chemical substances as well as of flotation collectors, flocculants and frothers and including a sulfiding agent to improve the separation of the copper mineral values from said slurry by froth flotation, the improvement comprising pre-determining a range of oxidation-reduction potentials developed in a slurry of the ore beneficiated with said chemical substances to a condition of high flotation yield of mineral values therein, and then modifying the quantity of said beneficiating chemical substances supplied to said slurry to continuously maintain an oxidation-reduction potential of said slurry in the same pre-determined high flotation yield range as the flotation proceeds.
 11. The method as defined in claim 10 wherein the sulfiding agent is selected from the group consisting of hydrogen sulfide, alkali metal hydrosulfide and alkali metal sulfide.
 12. The method as defined in claim 11 wherein the alkali metal component of said alkali metal sulfides is sodium.
 13. The method as defined in claim 10 wherein the sulfiding chemical component is sodium sulfide.
 14. The method as defined in claim 10 wherein the flotation collector is an alkyl xanthate.
 15. The method as defined in claim 10 wherein the flotation of said slurry to recover mineral values from the copper ore is performed by flowing said slurry through several of a series of flotation cells, each cell having a pre-determined range of oxidation-reduction potentials developed for the slurry beneficiated to a condition of high flotation yield of mineral values for that cell, and the quantity of beneficiating chemical supplied to the slurry of each cell is adjusted to maintain the said range of pre-determined oxidation-reduction potentials for that cell.
 16. The method as defined in claim 10 wherein the flotation of said slurry to recover mineral values from the copper ore is performed by flowing said slurry through a series of several flotation cells, each operating to remove mineral values by flotation, the first cell being a Maxwell cell for effecting primary recovery of the mineral values and the subsequent cells of the series being Fagergren cells operative to clean up additional values by flotation from the remaining ore slurry, each cell having the oxidation reduction potential of its slurry, the continuously flowing ore slurry therein continuously measured, and the beneficiating chemical added to the slurry passing to each of said cells being independently varied in quantity to maintain the pre-selected oxidation-reduction potential for each cell.
 17. The method as defined in claim 16 wherein the requisite quantity of beneficiating chemical added to each cell is automatically controlled to be independently supplied to the slurry being floated in each cell in quantity responsive to the pre-selected range of oxidation-reduction potentials of each cell of said series.
 18. The method as defined in claim 10 wherein the copper ore is predominately sulfidable compounds of copper other than copper sulfide.
 19. The method as defined in claim 10 wherein the copper ore is predominately oxides of copper.
 20. In a system for the beneficiation of a copper ore comprising copper sulfide and other sulfidable particles of copper mineral by addition to a slurry of said ore of oxidizing or reducing chemical substances as well as of flotation collectors, flocculants and frothers and including a sulfiding agent to improve the separation of the copper mineral values from said slurry by flotation, said froth flotation being performed in a series of flotation cells, said beneficiatng chemical substances being added to said ore slurry to adjust its flotation condition in each flotation cell, the improvement comprising predetermining a range of oxidation-reduction potentials developed in the slurry of the ore being benificiated with said chemical substances to a condition of high flotation yield of mineral values for each cell, and then controlling the quantity of said beneficiating chemical substances supplied to said slurry passed to each cell to maintain an oxidation-reduction potential of said slurry in each cell in the said predetermined high flotation yield range as the flotation proceeds. 